<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="./vue.js"></script>
</head>
<style>

</style>

<body>
  <div class="app">
    <input type="text" v-model="val">
    <h1>{{val | trim}}</h1>
  </div>
  <script>
    new Vue({
      el: ".app",
      data() {
        return {
          val: ""
        }
      },
      filters: {
        trim(val) {
          return val.replace(/ /g, "");
        }
      }
    })
  </script>
</body>

</html>